Add missing configuration values for RGB underglow

app/boards/shields/corne/corne.conf

@@ -1,5 +1,6 @@
 # Uncomment the following line to enable the Corne RGB Underglow
 # ZMK_RGB_UNDERGLOW=y
+# CONFIG_WS2812_STRIP=y
 
 # Uncomment the following line to enable the Corne OLED Display
 # CONFIG_ZMK_DISPLAY=y

app/boards/shields/kyria/kyria.conf

@@ -7,3 +7,4 @@
 
 # Uncomment the following line to enable RGB underglow
 # CONFIG_ZMK_RGB_UNDERGLOW=y
+# CONFIG_WS2812_STRIP=y

docs/docs/feature/underglow.md

@@ -21,10 +21,12 @@ Here you can see the RGB underglow feature in action using WS2812 LEDs.
 
 ## Enabling RGB Underglow
 
-To enable RGB underglow on your board or shield, simply enable the `ZMK_RGB_UNDERGLOW` configuration value in the `.conf` file of your user config directory as such:
+To enable RGB underglow on your board or shield, simply enable the `ZMK_RGB_UNDERGLOW` and `CONFIG_X_STRIP` configuration values in the `.conf` file of your user config directory as such:
 
 ```
 CONFIG_ZMK_RGB_UNDERGLOW=y
+# Use the STRIP config specific tot he LEDs you're using
+CONFIG_WS2812_STRIP=y
 ```
 
 If your board or shield does not have RGB underglow configured, refer to [Adding RGB Underglow to a Board](#adding-rgb-underglow-to-a-board).
@@ -114,8 +116,10 @@ Once you have your `led_strip` properly defined you need to add it to the root d
 };
 ```
 
-Finally you need to enable the `ZMK_RGB_UNDERGLOW` configuration value in the `.conf` file of your board (or set a default in the `Kconfig.defconfig`):
+Finally you need to enable the `ZMK_RGB_UNDERGLOW` and `CONFIG_X_STRIP` STRIP configuration values in the `.conf` file of your board (or set a default in the `Kconfig.defconfig`):
 
 ```
 CONFIG_ZMK_RGB_UNDERGLOW=y
+# Use the STRIP config specific tot he LEDs you're using
+CONFIG_WS2812_STRIP=y
 ```